1. Field of the Invention
The present invention relates to a method of controlling a cavity lamp of a microwave oven, and more particularly to a method of controlling a cavity lamp of a microwave oven which automatically or manually turns off the cavity lamp that had been previously turned on when a door was opened, so that life of the cavity lamp is lengthened and loss of electric power is reduced.
2. Description of the Prior Art
Generally, a microwave oven is an electronic product which cooks food by using a high-frequency wave emitted from a magnetron. The microwave oven has a melting function, a heating function, and a cooking function by multi-output of the magnetron. Also, the microwave oven has a grill cooking function in which the heater is used respectively in addition to the magnetron, a combination function in which both the heater and the magnetron are used simultaneously, and an oven function in which hot air is circulated in a cavity by a convection heater and a blowing fan installed in the rear portion of the cavity.
The microwave oven has a sensor-type automatic cooking control method and program-type automatic cooking control method. The sensor-type automatic cooking control method controls cooking time automatically by detecting humidity emitted from the food in accordance with heating by using a humidity sensor. Also, the program-type automatic cooking control method controls heating during an established predetermined cooking time in advance by experimentation in accordance with manual input of an amount of cooking in proportion to the kind of food and amount cooked.
The microwave oven, as shown in FIG. 1, is composed of a microprocessor 2 controlling the whole cooking operation, a key input portion 1 consisting of a matrix key in combination with key detecting port P.sub.0 .about.P.sub.2 and key scan port S.sub.0 .about.S.sub.2, and a cavity lamp CL installed in the cavity.
A user puts the food in the cavity and closes the door as a condition for the power to be supplied for cooking. Then the user presses an output key of the key input portion 1 to select output level and presses a start key after selecting a cooking function by pressing a particular cooking key. When the start key is pressed, a pulse signal is outputted to the key input portion 1 through the key detecting port P.sub.0 .about.P.sub.2 of the microprocessor 2 to be re-inputted through the key scan port S.sub.0 .about.S.sub.2. At this time the microprocessor 2 detects electric potential of the key input portion synchronized with the inputted pulse signal. Therefore, the microprocessor 2 outputs the control signal corresponding to the recognized key signal through the output port Q.sub.1, Q.sub.2.
When transistors TR.sub.1, TR.sub.2 are "on", the main relay RY2 and the sub-relay RY1 are driven. Accordingly, the cavity lamp CL is turned on and the magnetron MG is driven so that the high frequency wave is radiated into the cavity through the antenna, thereby the cooking is started. When the door is opened during cooking, the door open sensing switch D.O.M SW turns "off" so that operation of the microwave oven stops.
The cavity lamp CL is turned on during cooking to allow the user to observe the cooking condition of the food. Simultaneously, because the cavity lamp CL remains on even though the door opens, the user can easily put the food in/out before/after the cooking operation is performed.
However, before/after the door is opened, the cavity lamp CL always remains on. That is, when the user opens the door for a long time before starting to cook, or when the user opens the door for a predetermined time to remove vapor or smell in the cavity, the cavity lamp CL always remains on. Therefore, problem occurs that life of the cavity lamp is shortened, and loss of electric power is increased.